Color photographic light-sensitive materials generally are composed of a supporting base having thereon a red-sensitive silver halide emulsion layer containing cyan-dye forming couplers, a green-sensitive silver halide emulsion layer containing magenta-dye forming couplers and a blue-sensitive silver halide emulsion layer containing yellow-dye forming couplers, wherein cyan, magenta and yellow dye images are respectively formed upon exposure and color development with aromatic primary amino developing agents.
In particular, color camera films (both negative and reversal films) are prepared by coating on the supporting base (such as cellulose triacetate films, polyethylene terephthalate films, and the like) an antihalation layer, a red-sensitive layer, a green-sensitive layer, a yellow filter layer and a blue-sensitive layer.
The silver halide emulsions frequently used for such photographic materials were the so-called mixed emulsions, that is, emulsions comprising a combination of a more sensitive emulsion (containing coarse silver halide grains) and a less sensitive emulsion (containing fine silver halide grains) whereby a straight density-log exposure curve with extended exposure latitude can be obtained for each blue-, green- and red-sensitive layer.
It is known that the granularity of the dye image in color photographic materials depends mainly upon the size of the silver halide grains employed. Therefore, attempts to increase the sensitivity of the color photographic material by increasing the size of the silver halide grains (sensitivity of silver halide grains generally is proportional to the size of the silver halide grains) cause a coarsening of the granularity of the dye image.
British Pat. No. 923,045 describes a method for increasing the sensitivity of a color photographic material without coarsening the granularity of the dye image by providing the color photographic material with an uppermost more sensitive emulsion layer and a lowermost less sensitive emulsion layer, sensitive to the same region of the visible spectrum and each containing non-diffusing color couplers, with the maximum color density of the more sensitive emulsion layer being adjusted to be lower than that of the less sensitive emulsion layer, in particular from 0.20 to 0.60.
French Pat. No. 2,043,433 describes a method to improve the granularity in high-sensitivity color camera films (in such films the silver halide grains of the emulsion layers must be inevitably coarser) by providing the color photographic material with three emulsion layers sensitive to the same spectral region of visible light, the uppermost silver halide emulsion layer having the highest light sensitivity and the lowermost silver halide emulsion layer having the lowest light sensitivity, the uppermost and the intermediate layer each having a maximum density of 0.6 or less.
The Applicant has confirmed that such a three-layer structure, which consists of an uppermost, an intermediate and a lowermost emulsion layer respectively having a coarse, a mean and a fine grain structure, leads to an improved granularity in comparison with a two-layer structure, wherein the fine grain emulsion and the coarse grain emulsion are coated onto the base in this order, even if the average grain size and the distribution thereof are the same in both structures.
Unfortunately, when examining the structure of the developed image in a color camera film using such three-layer structure, some negative influence on the so-called adjacency effects (such as the Eberhard or vertical effect) was noticed. The adjacency effects, as known, are originated by an uneven development of two contiguous areas of a photographic material that receive exposures of different magnitude (the Eberhard effect being an increase in color density profiles with decreasing size when very small line images of varying sizes are photographed). Lack or decrease of such adjacency effects may adversely affect sharpness and brilliance of the developed image.